It is well known in the prior art that ventilating devices can be placed on the roofs of commercial buildings so as to draw air out of the building and allow input air to be introduced into the interior of the building. At least one example is known in the prior art, that shown in U.S. Pat. No. 4,149,590, of a device which includes a ventilator and an air conditioning unit in a common enclosure, to be mounted on the roof of a building, the enclosure also including provisions for heat exchange between the air going into and out of the building. In U.S. Pat. No. 3,270,738, a roof mounted heater is disclosed which includes a heat exchanger in it and which is adapted to be placed on the roof of a building.
There are also examples known in the prior art of devices which incorporate heat exchanging ventilating units into structural enclosures having particular features adapted to be installed in particular orientations in a building structure. Examples of devices which are adapted for such structural installations are shown in U.S. Pat. Nos. 3,256,930 and 4,048,811. Examples are also known in the prior art of particular structures which are especially designed so as to facilitate the installation of ventilating or heating equipment on the roofs of commercial buildings, such as those illustrated in U.S. Pat. Nos. 3,664,254 and 4,182,487.
The prior art is also cognizant of the use and structure of heat exchanging elements which include multiple layers of heat exchanging air passageways, with the passageways on each adjacent layer being oriented perpendicularly to the passageways on the next adjacent layer. Examples of patents illustrating such heat exchanging elements include U.S. Pat. Nos. 3,666,007, 4,051,898, and 4,099,928.